Til Death Do Us Part
by psychicallylinked
Summary: AU where FitzSimmons have been married since before joining the team and Coulson is the only one who knows. Will follow the AOS story line for the most part but will probably veer off at some point. Rated K for now, but the rating could change.
1. Chapter 1

**AU where FitzSimmons have been married since before joining the team and Coulson is the only one who knows. Will follow the AOS story line for the most part but will probably veer off at some point.** **Rated T. I'm not planning on having any M rated chapters at the moment, but things could always change.**

**Disclaimer: I do not own any of the Agents of SHIELD characters, and am writing this for entertainment purposes only.**

Jemma Simmons was nervous for her first day on the bus. Although it had been her who'd had to convince Leo that joining Coulson's team was an amazing opportunity, now that they gathering up all of their things and were moving them into the lab, Jemma couldn't help but have second thoughts. She could tell that Leo was nervous as well, and wasn't at all surprised when their nerves led to them bickering over the Night-Night Gun. They were stopped in their tracks, however, by a man in a suit who could only be a specialist, based on his attire and physique.

"FitzSimmons?" he asked in a tone that suggested he would rather be anywhere else at the moment. Without even thinking about it, Jemma immediately pointed to Leo and introduced him, while he did the same to her. It was something they'd been doing since their days at the Academy, and it was a very difficult habit to break. Agent Ward, who's identity had been confirmed when he'd mentioned Coulson, gave his comm receiver to Leo and looked thoroughly unimpressed when Leo proceeded to smash the device. Jemma just smiled, knowing how much Leo secretly loved to destroy things. Getting right to work, Jemma took a DNA sample from the inside of Ward's cheek while he was trying to ask about the comm receiver. She asked Ward if he was excited to be on the bus, and wasn't deterred by his sarcastic reply, keeping a smile on her face as she and Leo began the process of encoding the comm receiver.

It was two hours by the time they'd finished the process and then unpacked all of their supplies and safely stowed them away in the lab. All that was left to do was unpack their personal items and set up their bunk. Coulson had shown them where it was when they'd first entered the bus. While all of the other bunks were cramped and held tiny twin-sized beds, their bunk was slightly more spacious and held a double bed. It was still very small, but they were used to living in such conditions by now. The room even had two doors, so the rest of the team wouldn't become suspicious about why they stayed together. Coulson had known that they were married before he'd even asked them to join his team, and had been very accommodating.

It wasn't common for S.H.I.E.L.D. agents to get married, let alone for two of them to marry each other, but Jemma and Leo hadn't let that stop them. After all, they had never planned on entering the field, and had always thought that they would just stay in the lab. They had only been married a month when Coulson recruited them to his team, and very few people were even aware that they had gotten married. Of course, all the higher-ups knew, and it was in their files, but Jemma still went by Simmons, and they'd already been so close that their relationship hadn't really changed much. Jemma smiled as she placed their wedding photo atop their new dresser. It was her favourite one. She was wearing a simple white dress, and Leo had never looked more handsome in his tuxedo. They had their arms thrown around each other and had huge smiles on their faces. They'd both been so happy that day. They'd gotten married in England, at the quaint little church just down the road from Jemma's childhood home. Their families had been the only ones to attend, but the day had been perfect. Jemma twirled the necklace that held her wedding ring and sighed. She and Leo had agreed not to tell the team that they were married. It wasn't that they wanted to keep it a secret, they just didn't want to advertise it and they thought that it would be easier if the team didn't know. They were just putting the last of their things away, including their Doctor Who DVD collection, when Coulson knocked on their door and peered his head in.

"Briefing in five," he said, looking around their room. "I like what you've done with the place." With that he left, and they'd hurriedly put the finishing touches on their room before meeting the rest of the team. After getting the background information on Centipede, they headed to the site of the explosion with Agent May, where Leo was thrilled to finally get to use the D.W.A.R.F.s. They were like proud parents, watching them zoom around the destroyed lab, picking up things that could be easily missed by untrained eyes. This was what they loved about science; being able to build something that could do a job that no person could. Jemma was no longer nervous about their new team. She and Leo were quickly finding their place in the field.

Later, when Coulson demanded that they find some way to stop Mike Peterson without killing him, Jemma thought she was facing the impossible. Nevertheless, she and Leo did everything they could to find a solution. She'd pretended it was an exam. That was the only way she could keep thinking clearly. An exam was much more manageable than stopping a man from exploding and killing innocent people. She just had to stay calm. She heard Leo curse as his simulation again resulted in death, and she knew she had to keep him calm as well. They spoke the same language, and that was partly what made them such a great team.

They had finally managed to create a dendrotoxin that would have the desired affect on Mike Peterson, and as she ran into the train station, she only hoped that Leo would be able to reach Ward in time. She heard a shot ring out and saw Mike fall to the floor. Time felt as though it was moving in slow motion as she ran towards the man lying motionless on the floor. She felt for a pulse and checked his pupils before turning to Coulson and giving him a tired smile. She and Leo had done it. They had saved Mike Peterson. She had never felt so relieved in her life. Looking up to the balcony, she saw Leo give her a thumbs up from where he stood next to Ward.

After Mike had been taken into the ambulance and transported to a nearby hospital, the team returned to the bus. Coulson patted them on the back and told them that they had the rest of the day off. All Jemma wanted to do was eat Chinese food with Leo, and perhaps watch some Doctor Who. However, fate had other plans. They'd just started relaxing in the kitchen with their takeout and beer when the call came in about an 0-8-4 that S.H.I.E.L.D. wanted them to confirm. Ward called Coulson, who told them all to get some sleep and that they'd be taking off as soon as he got back to the airfield.

Jemma and Leo looked at each other with wide eyes. An 0-8-4! They couldn't believe it. They took the rest of their dinner to their bunk, where they both rambled on in excitement about what the 0-8-4 could be. They finally decided that it would be a good idea to try to get a couple hours of sleep before they reached their destination. As they laid in bed, Jemma curled around Leo with her head on his chest, it finally sunk in that their mission could be dangerous.

"Leo?" Jemma asked, tilting her head upwards to meet his eyes.

"Yeah, Jem?" he replied.

"Are you scared?" Leo paused for a moment.

"Of course I am, Jemma," he said. "But not of something happening to me. I'm scared something will happen to you. I don't think I could live with myself if I ever lost you." Tears pooled in Jemma's eyes as she reached up to kiss him.

"Don't worry," she said, breaking off the kiss. "I'm not going anywhere."

**Thanks for reading! Let me know what you think and I'll hopefully be posting the next chapter soon.**


	2. Chapter 2

**Hey guys! So here's chapter two! I've already gotten the third chapter written, so I'll post that soon. Enjoy!**

Jemma woke up to their alarm clock blaring at 7 a.m. She was curled into Leo, who groaned and tightened his arms around her waist when she tried to get out of bed.

"No Jemma. Five more minutes," he grumbled, burying his face in her neck. She sighed and pushed his arms off her waist. Damn Coulson and his request for a physical. She and Leo had been up until the early hours of the morning working. It wasn't their first late night; at the Academy, they had frequently sacrificed sleep in order to continue exploring an idea they'd had, and the bus was no different. That said, they'd been running on very few hours of sleep for a few weeks now, and Jemma knew that they would both benefit from sleeping in.

Unfortunately, Coulson had chosen this morning for his general physical and, as much as Jemma would have liked to stay in bed with Leo for another hour, she simply couldn't allow herself to be late for her meeting with Coulson. He was her boss after all, and tardiness was simply not in her nature. She quickly got dressed and gave Leo a kiss on the cheek before heading to the cargo hold to meet Coulson.

She knew she was about to have a bad day when she let the "a man of your age" comment slip out of her mouth. She immediately winced and played dumb when Coulson looked confused and stated that that was something you said to an old person.

After that, it was Ward complaining that the Night-Night pistol was still an ounce too heavy.

"I'm Agent Grant Ward," she imitated, "and I could rupture your spleen with my left pinky. Blindfolded." Skye laughed so hard that Jemma thought she was going to hurt herself. She made out the words, "you," "Fitz," "identical," and "psychically linked" between bursts of laughter before Ward came back into the lab. They all tried to keep a straight face. And failed.

"Is something funny?" Ward asked. Jemma searched quickly for an excuse.

"Poor, silly Fitz. He mistakenly left a dummy round in the pistol. Should be proper now."

They all watched as Ward brought the pistol up in a shooting stance, holding their breath.

"Great. Thanks." He said, and left the lab. He'd barely made it out before the three of them burst out laughing.

...

Jemma and Leo were both at a loss for how a dead man could be found floating in the air. They both rambled out theories when Coulson asked, but neither of them actually had any idea. It was the most interesting case they had encountered in their careers.

When she was examining the body back in their lab, Jemma was fascinated by the way the man had died. It was terrible of course, no one deserved to die like that, but fascinating nonetheless. Leo didn't exactly agree. He'd always had a weak stomach, and got freaked out when she performed autopsies. She wasn't surprised when he refused to enter the lab, choosing instead to stay in the cargo hold. Coulson commented on it and assumed he was afraid. Of course, Leo heard his comment and yelled that it was the smell that bothered him.

"There's no shame in it, Fitz. It's perfectly natural to be afraid."

"Hey. No! The only thing I'm afraid of is putrid, decaying flesh corrupting my pristine workspace." Jemma couldn't help but roll her eyes. "Do you remember the last time you brought a dead thing into the lab?"

"Oh, not the stupid cat again."

"The cat-"

"And it's _our _lab Fitz-"

"Tell him about the cat-"

"It's not your lab-"

"You left his liver next to my lunch!"

Coulson finally interrupted them and Jemma went back to giving her autopsy report. It wasn't long before May came in declaring the kid from the scene to be clean. Then Leo interrupted them with another electrostatic event.

...

They finally figured out that it was an alien virus that was causing such strange deaths, and Jemma was tasked with finding a cure. During the process, she discovered that the virus spread through electrostatic shock. As she told Coulson this in excitement, she noticed the strange look he was giving her. It was almost sad. She continued on talking about the virus and was vaguely aware of Coulson leaving to stand outside the lab. She didn't understand what he was doing until he said that he's sorry and locked the door. That's when she turned to see the object behind her fall to the floor and realized why Coulson looked so sad. She's been infected.

Leo didn't take the news well. He threw himself into building a delivery mechanism for the anti-serum that she knew she might not even be able to create. He smiled as he showed her, and she could tell that he hadn't fully processed what the virus meant for her. She gave him a weak smile, more for his benefit than hers.

When they got married, she'd been so happy and excited at the thought of growing old with Leo, settling down and maybe even starting a family together. Now, that dream might be ending after only a few months together as a married couple. _The team doesn't even know we're married, _she thought. _Maybe we should tell them._ But she though that telling them might only make things that much harder in the end.

After the first two mice had pulsed and died, Jemma was starting to lose hope. Leo kept telling her that everything would be fine, but she no longer believed him. She snapped at him, and they started fighting. That wasn't how she wanted to spend what was left of her life, but she couldn't help it. He blamed her. She was the one who'd convinced him to join the team when neither of them had even passed their field assessments. She said that she didn't force him to follow her, but she knew that wasn't true. Leo had admitted to her once that he would follow her anywhere. He was yelling at her know about how they've always been together and she's always been by his side and suddenly she can't fight with him anymore. She loves him too much.

"You have to fix this." He was pleading with her now.

"I don't know how, Leo. The antibodies from the three firefighters aren't strong enough to fight this virus. It's born from alien DNA. There's no one to create an antiserum from because no ones actually survived this except-"

She realized suddenly that someone had survived it at the same time as Leo did. They also realized that if they could scrape some epithelial cells from the helmet that they would be able to create an antiserum. Before Jemma could say anything else, Leo took off running. A moment later he ran into the lab carrying the case that held the helmet.

"No! You can't be in here."

"Too late. Jemma, please. I can't let you do this alone."

"Leo, I don't know what you think you're doing, but-"

"I'm doing what we always do. We're gonna fix this. Together."

They quickly got to work, knowing that time was of the essence. Jemma finally allowed herself to be hopeful. Having Leo working beside her made her feel more calm, even if she was terrified that she would infect him. She was actually starting to believe that she would make it through this when she saw the blue light from the last mouse. That's when she knew it was over. She asked Coulson to tell her dad first, and then if she could have a moment alone with Leo. She knew what she had to do as the rest of the team went back upstairs, so she picked up the fire extinguisher and walked up behind him as he tried to come up with another way to save her. God, she loved him so much for trying.

"I'm so sorry, Leo. I love you," she whispered before hitting him on the head with the fire extinguisher. While he was down, she quickly left the lab and lowered the ramp of the cargo hold. Looking over the edge and seeing nothing but blue sky, Jemma felt peace. She would be saving the man she loved, as well as her team. She almost didn't let herself look back, scared that she would be unable to go through with it if she saw Leo, but she couldn't resist. He was at the door, trying to get it open. Although she couldn't hear what he was saying, she could tell it was her name. She knew she had to jump now, before she lost her nerve.

Her last thought was that she hoped he would find happiness.

...

After Ward had saved her and she'd left Coulson's office, Jemma made her way to the bunk she shared with Leo, terrified of what he would say to her. She'd barely opened the door before he pulled her inside, kissing her like there was no tomorrow. Which, for her, there hadn't been. She could feel the tears on his face and knew that they were mixing with her own. After they'd calmed down, they laid together in their bed for hours just holding each other, both of them afraid to let go. Finally, Leo spoke.

"I was going to do it. I had the antiserum, the chute, everything. I just couldn't get the straps on.

"Leo, please-"

"You know, maybe I couldn't have done the whole James Bond, in mid-air type thing."

"Leo, shut up! Ward did an amazing thing, yes, but it wasn't Ward by my side in that lab searching for a cure. It wasn't Ward giving me hope when I had none. It was you. You're the hero." Leo looked surprised. Then he brought his face closer to hers and kissed her gently.

"I love you, you know?"

"I love you too."


	3. Chapter 3

**So here's the next chapter! I was feeling in the Christmas spirit, so I decided to write a chapter that takes place at Christmas. I don't know when it would fit into the AOS time line, but it was something I wanted to write and I really enjoyed doing it. I'm thinking of writing some more chapters about scenes we didn't see in the show, so let me know what you think of this one!**

Jemma and Leo both got up at the crack of dawn on Christmas Eve. May had landed the bus in Boston late the night before, and Coulson had given the team three days off for Christmas. Since none of them really had much for family to celebrate with, Jemma and Leo had invited everyone to their apartment for a Christmas celebration. Having everyone to their home was going to be a challenge, though, seeing as they hadn't been there in months and most of the team still didn't know that they were married. None of them had questioned the fact that they lived together, though. They supposed it was because they were so close that the team just thought it was normal.

However, there were a lot of things to be done around the apartment to prepare for their guests. Jemma and Leo both loved Christmas, so they had plenty of decorations that needed to go up. They also needed to hide any evidence of their marriage. First, though, they went in search of a Christmas tree. Being Christmas Eve, they had a difficult time. Most of the trees left to be sold were awful. They were thin or were missing branches, and Jemma and Leo almost gave up on having a tree at all. But just as they were about to give up and head home, Leo spotted the perfect tree. It was small but full, and it would be the perfect size for their apartment.

They had some trouble getting the tree into their apartment, however. Leo held the bottom and Jemma the top, while they tried to manoeuver the tree up the stairs and through their narrow doorway.

"Lift it up, Leo! It's never going to fit on that angle."

"I think I know the right angle, thank you very much. Lifting it up is going to make it worse."

"If you'd just listen-"

"We need to just-"

Suddenly, the tree slipped through the door, knocking over an unsuspecting Jemma. Leo, who was equally surprised, fell forward and onto the tree.

"What the hell?" They both spoke at the same time. Then they just looked up at each other and laughed.

They finally got the tree set up and decorated, and Jemma went out to buy groceries while Leo put up their Christmas decorations. By the time Jemma returned, she would have never been able to tell that they hadn't visited their apartment in months. Tinsel hung over the door frames, there was fake snow on the counter tops, snowflakes hung from the ceiling, and a light up snowman sat beside their front door.

"Oh Leo, this looks amazing!"

"I think you're missing the best part," he said, smiling as he looked at something above her head. She followed his gaze and smiled.

"Well, I suppose we know what we have to do," she said, looking at the mistletoe.

"It is tradition, you know."

Jemma wrapped her arms around his neck and pulled him close.

"That settles it then," she whispered, bringing her lips up to meet his. Leo responded eagerly. They hadn't had much privacy on the bus, and now that they were alone they could finally be together in the way they wanted. She gasped as Leo's tongued touched her lips, and opened her mouth willingly. She realized it had been too long since they'd been able to touch each other without worrying about someone walking in. She relished in the feeling of Leo's mouth on hers and let her hands roam his body freely. When she reached a particularly sensitive spot, Leo moaned and pushed her back until she was resting against the door. She felt his lips leave hers and suddenly found a little moan escape her lips when he started kissing her neck.

"Leo," she breathed. He didn't stop, only moved his mouth up to her ear and gave it a gentle bite. It was getting harder and harder for Jemma to think clearly.

"Leo, I have to put away the groceries," she managed to croak out and he groaned but pulled away slightly. She could feel him breathing just as heavily as she was, and his lips were red and slightly swollen. Looking at his lips distracted her, and she moved away before she could let herself get lost in him again. She grabbed the bags from the grocery store and quickly started putting things away. She felt Leo come up behind her and put his hands around her waist. She leaned back into him, smiling, as she continued to unload the grocery bags. It wasn't until his lips met her neck that she groaned.

"You know, this would go a lot faster if you'd stop distracting me like that."

"But that wouldn't be nearly as fun." She shook her head at him, but quickly put the last few things into the cupboards before turning around and kissing him. Where their other kiss had been slow and passionate, this kiss was hot and desperate. Jemma took charge and backed him towards their bedroom, simultaneously running her hands under his shirt and up his chest. Leo didn't know what had gotten into her, but he certainly wasn't complaining as he opened their bedroom door and relieved her of her sweater. They moved towards their bed and Jemma squealed as Leo picked her up and threw her lightly onto the bed, following quickly and recapturing her lips. Their hands roamed over each other's body, and their clothes were soon hitting the floor.

"I love you, Jemma."

"I love you too, Leo."

...

They finally dragged themselves out of bed around 2 o'clock in the afternoon, when they could no longer ignore their rumbling stomaches. Jemma smiled as she watched Leo make pancakes, one of the few dishes he could make without any major disasters. After they'd eaten, they set to work erasing all evidence that they were married. It wasn't too difficult; they mostly just had to hide their wedding photos, which they shoved in their closet, and make it look like Leo still lived in his old room and not in hers, which wasn't hard because a lot of Leo's things were still in there. They spent the rest of the day watching the Doctor Who Christmas specials and drinking eggnog.

The team came the next afternoon. They'd all still been staying on the bus as none of them lived in Boston, and therefore all came at the same time. Coulson brought wine, Skye brought Christmas sweaters for them all (the rest of the team had already been forced into them), Ward brought salad (that had likely been shoved into his hands by Skye), and May brought a pie that she'd apparently made herself (this admission got shocked looks from the rest of the team). They'd all exchanged pleasantries, feeling slightly awkward being in such a casual setting, before settling down to eat dinner. The evening passed with quickly, with Skye and Ward getting caught under the mistletoe before blushing and hurrying away from each other, Coulson and May getting more buzzed off the alcohol than they'd care to admit, and Jemma and Leo telling stories of their past Christmases together. This eventually led to Skye looking at all of the pictures on their mantle and commenting loudly about how cute they looked together.

"Is this from our mission in Peru?" She was looking at the selfie they had taken in front of the pyramid before examining the 0-8-4. They had just put that picture up the day before to replace one of their wedding photos.

"Yeah, we took that before everything went to hell," Leo commented darkly. "Hey, did you guys know that Peru has 32 different species of monkeys?"

"Oh, that reminds me! I've gotten gifts for you all." Jemma went into their bedroom to retrieve the gifts she'd gotten the team. She had stumbled across them yesterday when she'd gone to the grocery store and couldn't resist. As she brought them out, she apologized. "I'm sorry they're not wrapped." She started with Leo, handing him the metal ornament intricately detailed to look like a monkey. She'd gotten his name engraved on the front with "Happy Christmas! Love Jemma" on the back. She'd done the same for the rest of the team. Skye's ornament was a laptop, May's an air plane, Ward's a gun, and Coulson's a car that looked quite similar to Lola. She also held up an ornament shaped like a beaker that she'd bought for herself. She and Leo placed their ornaments on their tree while the rest of the team thanked her for their gifts.

As Jemma sat next to Leo on their couch, with the rest of her team talking and laughing around her and the room bathed in the glow from the lights on their Christmas tree, Jemma couldn't help but feel that it truly was a merry Christmas.


End file.
